A. Technical Field
The present invention relates to a sensor, and more particularly, to a device having multiple sensors integrated into a low cost compact package.
B. Background of the Invention
Conventional accelerometers and gyroscopes have been widely applied to measure acceleration and rate of rotation of an object, where an accelerometer and gyroscope are implemented in the object by micro-electro-mechanical-systems (MEMS) technology. The object may include various handheld devices, such as cell phones and electronic game controllers. FIG. 1A shows a schematic diagram 100 of a conventional sensor package having a gyroscope and an accelerometer for measuring the motion of an object in 6-degrees of freedom. As depicted, the conventional sensor package includes: a MEMS wafer 102 having an accelerometer and a gyroscope for measuring the acceleration and angular rate of an object; a glass interposer 104 bonded to the MEMS wafer 102 by a sealing mechanism; a dielectric layer 106 attached to the glass interposer 104; a flip chip Application Specific Integrated Circuit (FC ASIC) 122 attached to the dielectric layer 106 by one or more flip chip solder bumps 124; and a ball grid array (BGA) 120 for electrically connecting the package 100 to a circuit board (not shown in FIG. 1A).
FIG. 1B shows the bottom view of the sensor package 100. As depicted, the dielectric layer 106 may include traces 132 for connecting the BGA 120 to the FC ASIC 122 and FC solder bumps 124.
The glass interposer 104 may be formed of a glass. The signal from the accelerometer and gyroscope is transmitted to the FC ASIC 122 through the vias 108 and 110 and flip chip solder bumps 124. The FC ASIC 122 includes electrical components to process the signal readout of the accelerometer and gyroscope.
The convention sensor package 100 has several drawbacks. First, it includes the glass interposer 104, which increases the form factor of the package in the z-direction (height) and the manufacturing cost of the package. Also, the glass interposer 104 includes vias 108, increasing the fabrication cost and structural complexity. Second, the solder balls of the BGA (or, equivalently, pins) 120 should be large enough to provide sufficient standoff, D, so that the FC ASIC 122 would not touch the surface of circuit board to which the BGA 120 is soldered. This size requirement for the BGA 120 adds extra form factor in the z-direction. Third, if additional pins are to be implemented, the x-y footprint of the package 100 should be increased to accommodate the additional pins since the x-y footprint of the FC ASIC 122 cannot be compromised. Thus, the x-y footprint of the package 100 is determined by the dimension of the glass interposer 104, not by the dimension of the FC ASIC 122, increasing the overall form factor of the package 100.
Therefore, a better solution is needed to address the main issues, including the form factor, manufacturing cost, and structural complexity of the conventional sensor package.